1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member including a surface layer made of hydrogenated amorphous silicon carbide (hereinafter also referred to as “a-SiC”), and an electrophotographic apparatus including the electrophotographic photosensitive member. The surface layer made of hydrogenated amorphous silicon carbide is hereinafter also referred to as “a-SiC surface layer”.
2. Description of the Related Art
In an electrophotographic apparatus, a surface of an electrophotographic photosensitive member on which a photoconductive layer (photosensitive layer) is provided is charged, and then an image exposure light is applied to form an electrostatic latent image on the surface of the electrophotographic photosensitive member. Further, toner is applied to the electrostatic latent image on the surface of the electrophotographic photosensitive member to form a toner image, and the toner image is transferred to a transfer material such as paper to form an image. After the electrophotographic apparatus thus forms the image, a part of the toner remains on the surface of the electrophotographic photosensitive member. Thus, the residual toner needs to be removed. Generally, residual toner is removed in a cleaning process using a cleaning blade, a fur brush, or a magnet brush, and is typically removed in a cleaning process using a cleaning blade.
However, in recent years, toner having a smaller average particle size than conventional has been used for higher image quality, and it has become difficult to remove residual toner in the cleaning process. Specifically, to clean the residual toner having a small particle size, for example, pressing pressure of a cleaning blade needs to be increased. This may cause a burr of the cleaning blade or an increase in running torque of an electrophotographic photosensitive member. To solve the above-described problems, Japanese Patent Application Laid-Open No. H9-297420 proposes a method in which in an electrophotographic photosensitive member having a photosensitive layer of amorphous silicon, a surface of a conductive substrate that forms the photosensitive layer is previously made rough by a cutting or a rotation ball mill apparatus. Japanese Patent Application Laid-Open No. 2001-330978 proposes a method of controlling microscopic surface roughness Ra in a range of 10 μm×10 μm of an electrophotographic photosensitive member to a predetermined value to effectively prevent toner application.
As described above, effective cleaning of residual toner has been conventionally improved. However, the market's demands for image quality have been further increased. In particular, there is a significant demand for image quality in the market of print-on-demand (hereinafter also referred to as “POD”) such as near-print or a pictorial field. For example, minute fluctuations in concentration (a banding phenomenon) due to irregular rotation of the electrophotographic photosensitive member or a minute cleaning failure, which have not been heretofore problems, cannot be accepted.
To effectively clean residual toner, adjustment items such as the material, hardness, or pressing pressure of a cleaning blade, the shape or material of a surface of an electrophotographic photosensitive member, the material or particle size of toner, the material or amount of an external additive need to be appropriately adjusted. However, when toner having a small particle size is used, such a setting range may be reduced, and sufficient design latitude cannot be obtained, which may prevent design. Also, repeating image forming may gradually change activity of the surface of the electrophotographic photosensitive member depending on set values of the adjustment items, which may increase running torque of the electrophotographic photosensitive member. This phenomenon is expected as described below. A discharge product formed in or near a charger changes activity such as surface free energy of the surface of the electrophotographic photosensitive member. Thus, it is supposed that substances existing near the electrophotographic photosensitive member such as toner, a toner external additive, paper dust, or binder resin of an intermediate transfer body in some cases are easily applied to the surface, then a friction force between the surface of the electrophotographic photosensitive member and a cleaning blade changes. The increase in running torque may prevent smooth rotation of the electrophotographic photosensitive member, and cause a banding phenomenon. In particular, when the substrate processing as described in Japanese Patent Application Laid-Open No. H9-297420 is not performed, the banding phenomenon tends to easily occur.
Even when the substrate processing is performed, the substrate processing is effective in an initial stage, but a long-term use may increase running torque of the electrophotographic photosensitive member and cause a banding phenomenon or a cleaning failure. In Japanese Patent Application Laid-Open No. 2001-330978, only microscopic roughness of a substrate is considered, and using toner having a small particle size or a long-term use may increase running torque of an electrophotographic photosensitive member or cause a banding phenomenon.